I have had problems to generate pixel art for a game where units are of specific sizes such as 55x55 (not geometry but by pixels i.e. 55 pixels by 55 pixels). I have tried Gimp where I have misread many-times the sizes with the select tool -- it is irritating to get a bit too distorted size. Then I have used Inkscape that works actually quite good -- you generate the vector-image and select it and then you go to
"Export to bitmap" where you can specify the size (this same feature is probably also in Blender, probably as easy). Anyway I am looking for something more powerful like having helper color-palettes easily or automatically-done perhaps like here with Gimp. I can find a variety of tools mentioning pixels but I hope you to point out the best before trying all of them.
$ apt-cache search pixel|wc 99 861 6029